Combined propellant charge and bullet unit for well



F. V. PORTER A ril 2, 1968 COMBINED PROPELLANT CHARGE AND BULLET UNIT FOR WELL Filed Oct. 23, 1965 INVENTOR FORREST V. PORTER BY United States Patent ()fifice 3,376,375 Patented Apr. 2, 1968 3,376,375 COMBINED PRGPELLANT CHARGE AND BULLET UNIT FGR WELL Forrest V. Porter, Houston, Tex., assignor to Dresser Industries, Inc, Dallas, Tex., a corporation of Delaware Filed st. 23, 1965, Ser. No. 503,521 7 Claims. (Cl. 175-4.58)

ABSTRAtIT OF THE DISCLOSURE A combined propellant charge and bullet unit assembly for use in bullet perforating guns wherein the assembly includes a cup-shaped housing having an opening in the bottom thereof, a contact base disposed in the bottom of the cup-shaped case and covering the opening and adapted to engage an ignition member carried by the gun, a filament wire operably connected with the contact base and connected with a strap grounding the filament wire to the bullet gun, an insulating member placed between the filament wire and the contact base, an annular pelletized propellant charge positioned in the case relatively above the filament wire, an easily ignitable powder surrounding the filament wire in the center of the annular pellet, a seal member covering the open end of the case and having a central passageway the-rethrough, and a bullet positioned in the central passageway of the seal member with its rear end located adjacent the loose powder, whereby the powder is ignited by electrical energy and, in turn, ignites the charge to .propel the bullet from the gun.

This invention relates to bullet perforating guns utilized in oil field operations and more particularly to an improved combined propellant charge and bullet unit as sembly therefor.

Although bullet perforating guns have been used in perforating wellbore casings for many years, the design of such guns are fraught with many difficulties not ordinarily found in ballistics practised above the surface. For example, the diameter of the gun body is extremely limited. It has to be run inside oilfield casing which in many cases has an inside diameter of around and, in cases of tubing, even less. This results in a gun body with an over-all diameter of 4" and an effective barrel length of only about 2". With a standofi from zero to 1 /2" maximum, the bullet then has to penetrate a steel casing and several inches of cement before it reaches its ultimate target, the formation where it is expected to penetrate many more inches.

Among the numerous problems encountered in the design and construction of uniformly eflicient and effective bullet perforating guns, are those of securing adequate effective barrel length for the bullet, the mounting of the bullet in such a manner as to provide an effective seal is long as possible, as well as maintaining the relation between the bullet and propellant charge that maximum ballistic efiiciency of the gun is obtained. It is also desirable to provide a combined propellant charge and bullet unit assembly which may be preassembled under factory supervision and control, which may be stored a reasonable length of time, which may be safely transported to the field and installed in the bullet perforating gun with a minimum of time and effort and which has an efiicient ignition system producing a uniform burning of the propellant charge with a resultant maximum of uniformity in characteristics of operation.

F. V. Porters U.S. Patent 2,953,971, dated Sept. 27, 1960, discloses a bullet perforating gun taking most of the above features as well as others into consideration and properly weighing them to produce a bullet perforating gun which is being used successfully in commercial field operations. The present invention is directed primarily to providing an improved combined propellant charge and bullet unit assembly which has an improved ignition system.

It is an object of the present invention to provide an improved ignition system for a combined propellant charge and bullet unit assembly used in bullet perforating guns.

It is another object to provide an improved combined propellant charge and bullet unit assembly for bullet perforating guns, which permits the bullet to be placed further in the rear, thereby increasing sectional density.

It is a further object to provide an improved combined propellant charge and bullet unit assembly for Well perforating guns which increases the effective barrel length of the gun.

It is still a further object to provide an improved combined propellant charge and bullet unit assembly which is economical to manufacture, capable of reasonable shelf life, safe to transport and easy to load. In order to accomplish the above objects, and other objects which will become apparent from the detailed description to follow, the improved combined propellant charge and bullet unit assembly of the present invention is formed'of a cup-shaped cartridge case, an electrical igniter assembly is positioned in the case, a few grains of explosive are placed around the bottom of the igniter assembly, a pressed annular-shaped propellant pellet is placed on top of the bottom of the igniter assembly, a shear disc having a central bore seals the top of the case and a bullet is positioned in the central bore. The combined propellant charge and bullet unit assembly are placed in the charge chamber of the gun. An electrical igniter pin contacts the charge case which energizes the igniter assembly, detonating the explosive which, in turn, ignites the propellant pellet providing the energy for propelling the bullet.

A preferred embodiment of the invention is illustrated in the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a typical bullet perforating gun positioned in a Wellbore, the gun incorporating the present invention.

FIG. 2 is an enlarged cross-sectional view of the improved combined propellant charge and bullet unit assembly of the present invention.

FIG. 3 is a perspective view of the charge case showing the relationship of the igniter assembly.

Referring now to the drawings, and, in particular, to FIG. 1, it can be seen that a bullet perforating gun assembly 10 is comprised of a generally cylindrical tubular gun body 12 having a plurality of individual guns 14. The assembly 10 is adapted to be lowered into a well borehole 16 by a conductor cable containing an insulated conductor or conductors through which the firing of the individual guns 14 may be controlled. For a more complete general description of the over-all bullet perforating gun and its operation, reference is made to U.S. Patent 2,953,971. If desired, the gun assembly 10 may be also in the form shown in my copending application S.N. 412,487 filed Nov. 19, 1964, now Patent No. 3,327,793.

The gun body 12 may be formed of a generally elongated substantially solid steel cylinder of suflicient strength and solidity to withstand the pressures generated by the firing of the gun. Thegun body 12 is provided with a plurality of laterally extending coaxial bores 26 and 28. The smaller diameter bore 26 extends innermost and forms the charge chamber for each gun 14. Positioned in the charge chamber 26 is a combined propellant charge and bullet unit assembly 34. A bore 36 having an initial tapered portion 38 extends from the rear wall of the charge chamber 26 to a cylindrical recess or cavity 40 in the peripheral wall of the gun body 12. The tapered portion 38 of the bore 36 accommodates the tapered head 42 of a firing pin 3 44 which extends through the bore 36 into the cavity 40 where the electrical connection to the firing pin 44 is made to conductor 46. The tapered head 42 and the firing pin 44 are insulated from the gun body. A seal 48 is engaged with the wall of the cavity 40 to form a seal for the cavity 40 and prevent the entrance of well fiuid into the gun 14.

The cylindrical wall of the outer bore 28 is formed into female threads to engage with the male threads of a generally tubular barrel member 50 which has a central bore 51. forming a barrel for the bullet.

The essence of the present invention resides in providing a regular bullet well perforating gun assembly of the above design with an improved combined propellant charge and bullet unit assembly with improved ignition means.

As previously set forth, the conditions under which a bullet perforating gun operates is far from optmium. The bullet fired by the gun is required to penetrate a /8" steel casing, a varying amount of cement, and then substantially extend into the formation itself, which may be hard. All of this is required from 'a gun having a two inch barrel, the end of which may be virtually in contact with the steel casing. Accordingly, it has been found desirable to have a pro-pellant charge of fairly heavy density. A 200 grain charge per cubic inch of charge chamber has been found satisfactory. Such a charge will produce an average pressure in a gun with a barrel of approximately 190,000 pounds which provides most satisfactory penetration. However, the high density pellet requires optmium ignition capability.

FIG. 2 shows the improved combined propellant charge and bullet unit assembly of the present invention. As can be seen, the assembly 34 is formed of a cartridge case 52 of a non-conductive material. The case 52 is cup shaped having a generally cylindrical side wall and a bottom wall 54. The bottom wall 54 is provided with a circular opening 56 through which the firing pin 44 may extend. Positioned in the case 52 against the bottom wall 54 and covering the opening 56 is a metal contact base 58 having a tab 60 extending from one end. Attached to the tab 60 is a filament wire 62 which meanders across the contact base 58 and is attached to a strap 64. Between the filament wire 62, strap 64 and contact base 58 is an insulator 66 so that an electrical path extends from the contact base 58 through the tab 60 and along the wire 62 and strap 64 and not short circuited. The strap 64 extends upward along the cylindrical wall of the case 52 and bends over the top thereof. A few grains of an ignition type powder may be sprinkled over the filament wire 62.

An annular pellet 68 formed of consolidated propellant powder is inserted into the cartridge case 52 on top of the filament wire 62. To assure good contact, the base of the pellet may be coated with an appropriate cement and then the pellet 68 pressed into position and the cement allowed to dry before the remainder of the assembly of the unit is completed. The pellet 68 has a central passage 70 and a small amount of ignition type powder 72 or a mixture of black powder with ignition type powder 72 is poured into the central passage 70. A cotton wad 74 is placed on top of the powder 72.

A lid 76 forming a gas seal for the unit is placed over the open end of the cartridge case 52. The lid 76 has a center portion 78 of increased thickness which is provided with a central bore in which is positioned a bullet 80. This completes the unit 34.

The unit 34 is positioned in the charge chamber 26 of the gun 14. The head 42 of the firing pin 44 makes contact with the contact base 58. The end 82 of the strap 64 contacts the wall of the chamber 26 and provides the ground for the filament wire 62 through the strap 64.

As previously set forth, bullet perforating guns operate under adverse enviromental conditions, and it is necessary to have all factors at an optmium. In some instances, it is necessary to use high temperature propellant in which case the propellant is more difficult to ignite. Also, the propellant is pelletized and high density loads are desired. Again the pellet is difficult to ignite.

However, with the ignition system of the present invention, it has been found that good ignition is obtained for high density and high temperature pellets.

When firing pin 44 is energized, it, in turn, energizes the filament wire 62 through the contact base 58. The filament wire 62 heats and ignites any powder sprinkled on it and the loose powder 72 in the center of the pellet 68. The powder 72, being an easily ignitible powder, burns rapidly. The ignition of the pellet 68 starts in the bottom of the central passage 70 and works its way up. It has been found that such type of ignition is very desirable and effective resulting in good ignition for the pellet 68 and therefore resulting in the generation of sufficient gas to obtain good velocity of the bullet 80;

It has also been found that by using such construction the bullet 80 can extend back further in the case 52 which, in effect, increases the loading density of the charge, there being less area in the charge chamber. Also by being fur: ther back, the length of time that the bullet 80 is under seal is increased, and, in effect, there is an increase in the effective barrel length of the gun. All of these factors aid in increasing the over-all effectiveness of the gun.

I claim:

1. In a bullet perforating gun formed of a generally cylindrical gun body provided with at least one laterally extending opening forming an individual gun, each gun having an inner portion forming a charge chamber aecommodating a combined propellant charge and bullet unit assembly, an enlarged outer portion in which is removably secured a generally tubular barrel member having a barrel receiving the bullet, and electrical ignition means extending into the rear of the charge chambers, the improvement comprising an improved combined propellant charge and bullet unit assembly formed of:

a cup-shaped cartridge case formed of nonconductive material having a generally cylindrical side wall and a bottom wall,

a circular opening in the bottom wall;

a contact base of conductive material positioned against the bottom wall of the case and covering the circular opening,

a tab extending from the contact base,

a filament wire attached to the tab meandering across the extent of the bottom;

an insulator between the filament wire and the contact base;

a strap of conductive material extending upward along the cylindrical wall of the case and folding overthe top thereof and contacting the wall of the charge chamber;

an annular pelletized propellant charge positioned in the case in contact with the filament wire,

a quantity of loose easily ignitible powder in the cen-- ter of the annular pellet;

a cotton wad covering the loose powder;

a seal disc having a central passage covering the open end of the case;

a bullet positioned in the central passage of the seal disc with its rear end contacting the cotton wad;

the contact base of combined propellant charge and bullet unit contacting the electrical ignition means in the gun whereby upon energization, the filament wire is heated which ignites the loose powder in the center of the pellet which in turn ignites the pellet.

2. In a bullet perforating ,gun formed of a generally cylindrical gun body provided with at least one laterally extending opening forming an individual gun, each gun having an inner portion forming a charge chamber accommodating a combined propellant charge and bullet unit assembly, an enlarged outer portion in which is removably secured a generally tubular barrel member ,having a barrel receiving the bullet, and electrical ignition means extending'into the rear of the charge chamber, the improvement comprising an improved combined propellant charge and bullet unit assembly formed of:

a cup-shaped cartridge case formed of nonconductive material having a generally cylindrical side wall and a bottom Wall,

a circular opening in the bottom wall;

a contact base of conductive material positioned against the bottom wall of the case and covering the circular opening,

a tab extending from the contact base,

a filament Wire attached to the tab extending across the bottom;

an insulator between the filament wire and the contact base;

a strap of conductive material extending upward along the cylindrical wall of the case and folding over the top thereof and contacting the wall of the charge chamber;

a quantity of loose easily ignitible powder around the filament wire;

an annular pelletized propellant charge positioned in the case on top of the filament wire,

a quantity of loose easily ignitible powder in the center of the annular pellet;

a cotton wad covering the loose powder;

a seal disc having a central passage covering the open end of the case;

a bullet positioned in the central passage of the seal disc;

the contact base of combined propellant charge and bullet unit contacting the electrical ignition means in the gun whereby upon energization, the filament wire is heated igniting the loose powder which in turn ignites the pellet.

3. In a bullet perforating gun formed of a generally cylindrical gun body provided with at least one laterally extending opening forming an individual gun, each gun having an inner portion formin a charge chamber accommodating a combined propellant charge and bullet unit assembly, an enlarged outer portion in which is removably secured a generally tubular barrel member having a barrel receiving the bullet, and electrical ignition means extending into the rear of the charge chamber, the improvement comprising an improved combined propellant charge and bullet unit assembly formed of:

a cup-shaped cartridge case formed of nonconductive material having a generally cylindrical side wall and a bottom wall,

a circular opening in the bottom wall;

a contact base of conductive material positioned against the bottom Wall of the case and covering the circular opening,

a tab extending from the contact base,

a filament wire attached to the tab extending across the bottom;

an insulator between the filament wire and the contact base;

a strap of conductive material extending upward along the cylindrical Wall of the case and folding over the top thereof and contacting the wall of the charge chamber;

a quantity of loose easily ignitible powder around the filament wire;

an annular pellctized propellant charge located in the case above the filament wire;

a seal disc having a central passage covering the open end of the case;

a bullet positioned in the central passage of the seal disc;

the contact base of combined propellant charge and bullet unit contacting the electrical ignition means in the gun whereby upon energization, the filament wire is heated igniting the loose powder which, in turn, ignites the pellet.

4. In a bullet perforating gun formed of a generally cylindrical gun body provided with at least one laterally extending opening forming an individual gun, each gun having an inner portion forming a charge chamber accommodating a combined propellant charge and bullet unit assembly, an enlarged outer portion in which is removably secured a generally tubular barrel member having a barrel receiving the bullet, and electrical ignition means extending into the rear of the charge chamber, the improvement comprising an improved combined propellant charge and bullet unit assembly formed of:

a cup-shaped cartridge case formed of nonconductive material having a generally cylindrical side wall and a bottom wall,

a circular opening in the bottom wall;

a contact base of conductive material positioned against the bottom wall of the case and covering the circular opening,

a tab extending from the contact base,

a filament wire attached to the tab extending across the bottom;

an insulator between the filament wire and the contact base;

a strap of conductive material extending upward along the cylindrical wall of the case and folding over the top thereof and contacting the wall of the charge chamber;

an annular pelletized propellant charge positioned in the case in contact with the filament wire, said pellet having a central passage;

a quantity of loose easily ignitible powder in the bottom of the cartridge case;

a seal disc having a central passage covering the open end of the case;

a bullet positioned in the central passage of the seal disc and extending into the central passage of the pellet;

the contact base of combined propellant charge and bullet unit contacting the electrical ignition means in the gun whereby upon energization, the filament wire is heated igniting the loose powder which in turn ignites the pellet.

5. An improved combined propellant charge and bullet unit assembly for a bullet perforating gun comprising:

a cup-shaped cartridge case formed of nonconductive material having a generally cylindrical side wall and a bottom wall,

a circular opening in the bottom wall;

a contact base of conductive material positioned against the bottom wall of the case and covering the circular opening,

a tab extending from the contact base,

a filament Wire attached to the tab meandering across the extent of the bottom;

an insulator between the filament wire and the contact base;

a strap of conductive material extending upward along the cylindrical wall of the case and folding over the top thereof;

an annular pelletized propellant charge positioned in the case in contact with the filament wire,

a quantity of loose easily ignitible powder in the center of the annular pellet;

a cotton wad covering the loose powder;

a seal disc having a central passage covering the open end of the case;

a bullet positioned in the central passage of the seal disc with its rear end contacting the cotton wad.

6. In a bullet perforating gun formed of a generally cylindrical gun body provided with at least one late-rally extending opening forming an individual gun, each gun having an inner portion forming a charge chamber accommodating a combined propellant charge and bullet unit assembly, an enlarged outer portion in which is removably secured a generally tubular barrel member having a barrel receiving the bullet, an electrical ignition means extending into the rear of the charge chamber, the improvement comprising an improved combined propellant charge and bullet unit assembly formed of:

a cup-shaped cartridge case formed of nonconductive material having a generally cylindrical side wall and a bottom wall;

an opening in the bottom wall;

a contact base of conductive material positioned against the bottom wall of the case and covering the opena filament wire having one end connected with the contact base;

a conductive member connected with the other end of the filament wire and extending outside the case to form a ground with the gun body;

an insulator located between the filament wire and the contact base;

a quantity of loose, easily ignitable powder around the filament wire;

an annular pelletized propellant charge located in said case;

a seal member having a central passageway covering the open end of the case;

a bullet positioned in the central passageway of the seal member; and,

the contact base of the combined propellant charge and bullet unit contacting the electrical ignition means in the gun whereby upon energization, the filament wire is heated igniting the loose powder which, in turn, ignites the pellet.

7. An improved combined propellant charge and bullet unit assembly for a bullet perforating gun comprising:

a cup-shaped cartridge case formed of non-conductive material having a generally cylindrical side wall and a bottom wall;

an opening in the bottom wall;

a contact base of conductive material positioned against the bottom wall of the case and covering the opena filament wire attached to thevcontact base and extending across the bottom wall of the case;

an insulator between the filament wire and the contact base;

a conductive member connected with the other end of the filament wire and extending to the exterior of the case;

an annular pelletized propellant charge located, in

said case;

a quantity of loose, easily ignitable powder in the center of the annular pellet around the filament wire;-

a seal member having a central passageway covering the open end of the case; and,

a bullet positioned in the central passageway of the seal member.

References Cited UNITED STATES PATENTS 2,358,951 9/1944 Turechek 175-458 2,946,283 9/1960 Udry 1754.5'9 X 2,953,971 9/1960 Porter 175-'4.58 3,180,221 4/1965 Porter l75-4.58

CHARLES E. OCONNELL, Primary Examiner.

DAVID H. BROWN, Examiner. 

